<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<form action="" method="post">
    {{msg}}
    <input type="hidden" name="id" value="{{stu.s_id}}">
    姓名: <input type="text" name="username" value="{{stu.s_name}}">
    年龄: <input type="text" name="age" value="{{stu.s_age}}">
    <input type="submit" value="提交">
</form>

</body>
</html>